In our original studies, we first described the ability to generate MHC class I restricted CD4+ T cells by retrovirally transduced normal T cells with MHC class I restricted TCR genes. We subsequently showed that if the TCR had sufficient affinity, the resulting MHC class 1 restricted CD4+ T cells could recognize physiologic levels of antigen expressed by tumor cells. Therefore, these novels T cells could augment the anti-tumor immune response by helping to prime the host immune response in tumor lesions. They could also promote the persistence and function of adoptively transferred CD8+ T cells. However, nothing is known about the biology of TCR transduced CD4+ T cells in vivo and their impact on the CD8+ T cells in vitro or in vivo. We have preliminary data that shows this novel population actually inhibits CD8+ T cell priming which would be contrary to their desired function. The goal of this project is to acquire a better understanding ofthe role of MHC class 1 restricted CD4+ T cells in anti-tumor immunity. Our central hypothesis is that MHC class I restricted, TCR transduced CD4+ T cells can be made to augment the antitumor immune response by CD8+ T cells. We predict this will occur by inducing them to become potent Th cells capable of licensing DC to prime CD8+ T cells in vitro. We further predict that MHC class I restricted, TCR transduced CD4+ T cells can be made promote the persistence and function of TCR transduced CD8+ T cells in vivo. These hypotheses/predictions will be tested using a combination of mouse and human CD4+ T cells transduced to express the TIL 13831 TCR. These TCR transduced CD4+ T cells, which recognize the tyrosinase:368-376 epitope presented by HLA-A2, will be compared to their normal mouse or human counterparts for their ability secrete cytokines, license DC to prime/activate naive and TCR transduced CD8+ T cells, and mediate tumor regression in vivo.